Oxidising agents
Oxidation is a chemical reaction in which a substance transfers electrons. Corrosion describes the structural degradation of materials, usually metals, through oxidative processes. However, oxidation can also occur without corrosion, for example in organic powders or dyes.
Oxidising agents are substances that specifically oxidise other substances by absorbing electrons themselves. Oxidising agents play a special role in powder technology because powders are highly reactive due to their large specific surface area. The finer the powder, the faster oxidative changes occur.
The most important oxidant is oxygen from the air. It can passivate or corrode metal powders. It breaks down fats, vitamins and flavours in food powders. Pigments, active ingredients and polymers also change under the influence of oxygen. Fine, porous or spray-dried powders are particularly sensitive.
In addition to oxygen, other oxidising agents can also be used. These include hydrogen peroxide as well as solid peroxides and per compounds. They are used, for example, for bleaching, disinfecting or chemically activating powders. Nitrates, chlorates and certain metal oxides also act as oxidising agents, some of which are very strong. In addition to oxygen and chemical oxidising agents, UV-activated systems can also be used.
UV radiation splits hydrogen peroxide or ozone, for example, and produces highly reactive hydroxyl radicals. These have a strong oxidising effect and are suitable for bleaching, disinfecting or activating powder surfaces.
In powder mixtures, the use of oxidising agents requires a high degree of process control. Inhomogeneous distribution, local overconcentrations or oxygen ingress can lead to safety risks. Depending on the application, oxidation must therefore be specifically enabled or consistently prevented. This is achieved, for example, by using inert gas-supported mixing machines. amixon® is a manufacturer of vacuum- and pressure-tight mixing systems.